1) ADHD people often don't get told upfront that there are many more options (20+) than just the first stimulant med prescribed. So when the first one doesn't suit them they tend to despair of all meds and not go back to ask for a different prescription. 2) doctors and ADHDers are often irrationally over-reluctant to combine meds, but some combinations have positive synergistic interactions which means you can get more beneficial effects on lower dosages of each so less side-effects or risks.